Question

急：已知x^2-5x-1=0,求根号x^2+1/x^2-11的值

Answer 1

x²-5x-1=0

两边同除x得：x-5-1/x=0

则：x-1/x=5

(x-1/x)²=25

即：x²-2+1/x²=25

则：x²+1/x²=27

所以,x²+1/x²-11=16

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